Rust-preventive composition



Patented June 1, 1948 2,442,581 RUST-PREVENTIVE COMPOSITION John W. Bishop, Crani'ord, N. 3.,

Water Associated Oil Company,

assignor to Tide Bayonne, N. J.,

a corporation of Delaware v No Drawing. Application July 28, 1945, Serial No. 607,677

This invention relates to compositions adapted to prevent the rusting of metals, particularly ferrous metals, as for example, the surfaces of machine parts, piston rings, machine guns, light arms, gears, the inside of steel drums, and the like, upon exposure to humid atmospheres or other atmospheres corrosive to metal.

The compositions of this invention comprise a minor proportion of a material effective for the prevention of rusting of ferrous metal surfaces and a major proportion of a suitable solvent vehicle for such material. The vehicle may be an oil, such as a hydrocarbon lubricating oil, or it may be any other suitable hydrocarbon or nonhydrocarbon substance. Compositions, according to this invention, which contain lubricating oils may be used in dual capacity as a lubricant and a rust-preventive, as for examle, in the lubrication of and prevention of rust formation on the interior parts of internal combustion engines.

The rust-inhibiting compositions of this invention contain products derived from oxazoline compounds by reaction with certain phosphoric acid esters. The oxazoline structure is known, one particularly eii'ective type thereof being the 2-oxazolines which contain the following radical:

l tH o I It is preferred to employ those oxazoline compounds in which one or more of the carbon atoms carries at least one relatively long chain alkyl group. Preferably, this long chain alkyl group is attached to the carbon atom between the nitrogen and the oxygen of the oxazoline ring. More specifically, such allryl oxazolines may be represented by the following structural formula:

N o l,

in which R, R1 and R2 may be hydrogen or alkyl and Re is alkyl. R3 is desirably of such'chain length as may be obtained as an alkyl residue 2 from a higher fatty acid. Examples of such compounds are the reaction product produced by reacting oleic acid with 2-amin0-2-methy1-lpropanol, and having the following formula:

and the reaction product of oleic acid with 2- amino-l-butanol or 2nitro-l-butanol, having the following formula:

Other oxazolines which may be suitable, and methods for their preparation, are known, for example, in United States Patents Nos. 2,372,409 and 2,372,410.

In preparing the composition of the invention, a suitable oxazolinecompound, as above defined, is reacted with an acid ester of a phosphoric acid, desirably a dialkyl ester of phosphoric acid in which the alkyl radicals contain a sufficiently high number of carbon atoms to impart good hydrocarbon solubility. For this purpose, the alkyl radicals should contain from about eight to about eighteen carbon atoms, and preferably from twelve to eighteen carbon atoms. In the reaction product, the acid phosphoric acid ester is thought to be in loose combination with oxazoline compound, as will be described in more detail hereinbelow. 1

The preferred procedure is to add separately to the oil or other suitable vehicle the desired acid phosphate ester and oxazoline compound. These two substances react mole for mole in the oil at room temperature to form, in solution, a loosely combined addition product. Indications are that during the reaction, a hydrogen oi the acid phosphate is transferred, to the nitrogen of the oxazoline compound, and a bond is iormed between the nitrogen and one of the-'o'xygehs of the phosphoric acid ester, the phosphoric acid ester and oxazoline nuclei otherwise remaining intact. As an illustration, by thus reacting a dialkyl acid phosphate with an oxazoline compound, for example, a compound of the formula:

hydrocarbon radicals, the addition salt formed may be represented by the formula:

In some cases, a slight excess of the phosphate ester may be used, with advantage, over that required for the reaction. Instead of the abovedcscribed method of preparation, the phosphoric acid ester and the oxazoline compound may be combined prior to addition to the vehicle and the resulting product then incorporated in the vehicle, if desired.

Although the composition which has just been described is highly active to prevent the rusting of metal surfaces under various conditions, considerable improvement can be obtained, regarding effectiveness under a wider variety of conditions, and at the same time certain economies can be effected when the composition contains, in addition to the described phosphoric acid ester-oxazoline compounds, certain metal sulfonates. The latter desirabl consist of alkali or alkaline eart' metal sulfonates, such, for example, as those derived from petroleum Inahogany acids. One particularly effective compound of the latter type is sodium sulfonate, a composition of which is known in the art as Petronate. When preparing compositions with sulfonate as one component, and using the described procedure of forming the oxazolinephosphate ester compound in the oil, it is important that the said compound be formed prior to addition of the sulfonate. This is to prevent reaction between the phosphate ester reactant and the sulfonate, which would result in removal of phosphate ester from the reaction mixture and prevent the desired combination with the oxazoline compound. Likewise, when using sulfonates, it will be found most practical to employ a ratio of phosphoric acid ester to oxazoline of not over about two moles of the former to one mole of the latter, in order to prevent undesired reaction between the sulfonate and any free phosphoric acid ester, which, it has been found, greatly reduce the effectiveness of the composition.

As indicated above, the active rust-inhibiting materials may be used in minor proportions in the compositions. For most uses, the total amount of rust-inhibiting additive material need not exceed about Smaller proportions are effective, for example, suitable compositions may be prepared using 0.25% of the phosphoric acid ester, 0.15% of the oxazoline compound 1 and about-1.6% and up of the sulfonate. Amounts of sulfonate up to about 20% have proved effective, although in most instances such large amounts are unnecessary. Other suitable compositions may employ from about 0.5% to 2.5%

or somewhat higher of the phosphoric acid ester with amounts of the oxazoline compound ranging from 0.4% to about 2% by weight. Compositions prepared from the phosphoric acid ester and the oxazoline in concentrations shown above, without sulfonate, are satisfactory for particular uses.

,The oxazolines, taken alone, are of relatively little or no effectiveness in the inhibition of rusting of steel surfaces. The phosphoric acid esters or the sulfonates, if taken alone, are only moderately effective in this respect. However, combinations of the phosphoric acid ester and oxazoline compounds in the compositions of the present invention are many more times effective than would be expected from a summation of the individual effectiveness of the components; and incorporation of the sulfonate component with the others results in further unexpected increase in rust-inhibiting effectiveness and other advantages. Coaction or interdependence between the additive components apparently causes these 'results. Inclusion of sulfonate with the phosphoric ester-oxazoline derivative permits use ofconsiderably less amounts of the latter to give the same rust-inhibitor effectiveness than would be required were no sulfonate present. This means a saving in cost since the sulfonates are relatively inexpensive as compared to the cost of the other stated additive.

.A further, and important, feature lies in the fact that these compositions form stable solutions. Obtainment of solution stability, as well as satisfactory inhibitor effectiveness, in compositions containing complex additives constitutes a major problem in the art. The present discovery of components having compatible solubility characteristics, as well as markedrust-inhibiting efi'ectiveness and other desired properties, is a major advance.

The nature of the coaction between the several components responsible for the high degree of rust-inhibition of the invention composition is not fully known, but such phenomenon obviously occurs. The additive materials are highly polar in character, which may account at least in part for their powerful rust-preventing properties. Presumably, this polarstructure is also responsible for an additional characteristic possessed by these compositions, which is their strong wetting action upon, and adherence to, metal surfaces to which they are applied. Modern usage of rust-preventive compositions of the type here concerned requires that they cling tenaciously to metal surfaces in a substantially unbroken film under quite adverse conditions, as when subjected to high temperature and humidity over extended periods, and in many cases when subjected to more corrosive atmospheres such as salt spray or mist. As compared to known rust-preventing compositions, the compositions of this invention adhere more tenaciously to metal surfaces and protect the same under a. greater variety of adverse conditions, as will be apparent from the tests disclosed hereinbelow.

The compositions are relatively non-hydrophilic and, thus, are not readily removed from surfaces by water.

The following examples and test data. will illustrate certain embodiments of the invention.

Example I In the stated humidity corrosion test, which is more fully described in Army-Navy Aeronautical Specification Compound; Corrosion-Preventive, Aircraft Engine, AN-VV-C-576a, Amendment 1, June 3, 1943, two freshly sand-blasted steel panels are coated on all surfaces with the test oil, drained for at least 4 hours in an atmosphere of 50-55% relative humidity at a temperature of 25 C., and then subjected to a circulating atmosphere of 95-100% relative humidity at a temperature of 120 F. for 150 hours in a special humidity cabinet. At the end of the test period, the panels areremoved from the humidity cabinet, cleaned with naphtha and examined. The presence of any corrosion on the panels, except within A; inch from any edge, evidences failure of the test oil.

The oil composition of this invention, described and prepared as in Example I, was subjected to the above-described humidity corrosion test and satisfactorily passed the same, i. e., the test panels, after being coated with the composition and exposed as described, were not corroded in areas more than inch from the edges thereof.

Example II In order to determine the effect of increasing the proportional amount of the phosphate esteroxazoline compound, an oil composition was made up by the procedure described in Example I, using as the reactants 2.5% of the dilauryl acid phosphate and 2.0% of the 2-amino-2-methyl-1- propanol-oleic acid reaction product in a petroleum lubricating oil. This represented a total additive content of 4.5% as contrasted with 1.25% in Example I.

The Example II composition also passed the above-described 120 F.-150 hour humidity test, but did not give particularly good protection in a similar but longer humidity test of 300 hours at 100 F. It did, however, pass a salt water immersion test and a salt spray test. In the salt water immersion test, a recognized procedure, described in paragraph F-d of U. S. Army Specification 2-122, was followed. Two sandblasted steel panels are totally immersed in the test oil, drained for 16 hours and then totally immersed for 20 hours in synthetic sea water. The test panels, after being removed from the sea Water and dipped in acetone, must show no corrosion, except within A; inch from any edge, if the test oil is to be considered as having passed this The salt water spray test, which likewise is a recognized procedure, comprises dipping three test panels of freshly sand-blasted steel in the test oil, draining the same overnight at room temperature, then exposing them at room temperature to a fine mist of 4% aqueous sodium chloride solution for 24 hours. Any corrosion on the panel surfaces, except within 4; inch of any edge, indicates failure of the test oil to protect against rusting under the test conditions.

The efiect of increasing the additive concentration is obvious since the Example I composition failed the salt water immersion test and the salt water spray test.

Example 11! This composition was prepared as described in Example I, except that only 0.5% of the dilauryl acid phosphate and 0.4% of the oleic acid-oxazoline product of Example I was incorporated in the hydrocarbon lubricating oil in this instance, and, after stirring until the resulting solution was homogeneous, 2.5% of Petronate" (60-65% sodium sulfonate) was dissolved therein.

.relatively long periods, is obtained in the Example III composition by incorporation of sulfonate although considerably less of the phosphoric ester-oxazoline compound is present than in the Examples I and II compositions.

Example IV In further illustration of the function of sulfonates in these compositions, a composition was prepared as follows. v

To a petroleum lubricating oil consisting of a blend of 50% solvent refined, acid treated, wax free neutral oil of 60 Saybolt seconds viscosity at 100 F. derived from coastal crude and 50% nonviscous Mid-Continent solvent treated neutral of S. U. S./ F., there were added 0.75% of dilauryl phosphate and 0.6% of the 2-amino-2- methyl-l-propanol-oleic acid reaction product described in Example I, with stirring. When the solution had become homogeneous, 8% of Petronate was added and dissolved in the oil composition.

The resulting composition, prepared as described in Example IV, and containing a greater proportion of metal sulfonate than the Example III composition, was subjected to all of the abovedescribed tests and passed each of them satisfactorily. This composition is, therefore, Well adapted for the prevention of rusting of metal surfaces, to which it may be applied, under a wide variety of severe exposure conditions. While certain compositions of the invention, prepared as described from, the acid esters of phosphoric acid and oxazolines together, without inclusion or the sulionate may aiford adequate protection under such conditions, the advantages, as regards inhibitor enhancement effect and economy fiowing from inclusion of the sulfonate component, are obvious from the above examples and test results.

It will be understood that the specific examples appearing hereinabove are illustrative embodiments and are not intended to constitute limitations upon the scope of the invention.

I claim:

1. A rust-preventive composition comprising a liquid hydrocarbon in major proportion having dissolved therein a minor proportion, sufiicient to substantially inhibit rusting of metal surfaces, of

a salt formed by an oil-soluble alkyl acid ester of phosphoric acid containing an alkyl group of about eight to about eighteen carbon atoms with the ring nitrogen of an oxazoline compound in which at least one of the ring carbon atoms carries a long chain alkyl group.

2. A rust-preventive composition comprising a liquid hydrocarbon in major proportion having dissolved therein a minor proportion, sufiicient to substantially inhibit rusting of metal surfaces, of a quarternary ammonium salt formed by an oilsolu'ble alkyl acid ester of phosphoric acid containing an alkyl group of about eight to about eighteen carbon atoms with the ring nitrogen of a long chain aliphatic-substituted oxazoline.

3. A composition effective to inhibit corrosion of metal surfaces to which it is applied, comprising a hydrocarbon oil in major proportion having dissolved therein a minor proportion, sufficient to substantially inhibit rusting of metal surfaces, of a quaternary ammonium salt formed by an alkyl acid phosphate containing an alkyl group of about 8 to 18 carbon atoms with an alkyl oxazoline containing at least one long chain alkyl group.

4. A composition effective to inhibit corrosion of metal surfaces to which it is applied, comprising a hydrocarbon oil in major amount and a minor but corrosion-inhibiting amount of a quaternary ammonium salt formed by an oxazoline of the following formula:

in which R, R1 and R2 are hydrogen or alkyl groups and R3 is a long chain alkyl group, with an oil-soluble dialkyl acid ester of phosphoric acid containing an alkyl group of about eight to about eighteen carbon atoms.

5. A rust-preventive composition, as defined in claim 2, which, in addition, contains an excess of said alkyl acid ester of phosphoric acid.

6. A rust-preventive composition comprising a hydrocarbon oil of lubricating grade in major proportion having dissolved therein a rust-inhibiting amount of a quaternary ammonium salt formed by an alkyl acid ester of phosphoric acid in which the alkyl groups contain from about eight to about eighteen carbon atoms with the ring nitrogen of an oxazoline compound containing a long chain alkyl group.

JOHN W. BISHOP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,146,584 Tipkin Feb. 7, 1939 2,285,855 gBaxter June 9, 1942 2,366,190 Hurn Jan. 2, 1945 2,372,410 Tryon Mar. 2'7, 1945 2,373,627 Dietrich Apr. 10, 1945 2,397,381 Smith et al Mar. 26, 1946 

